Titanium-based ceramic nanoparticles, i.e., titanium nitride nanoparticles (TiN-NPs) and titanium carbide nanoparticles (TiC-NPs), are used on counter electrodes (CEs) for quantum-dot-sensitized solar cells (QDSSCs). The QDSSC with TiC-NPs-CE exhibits the highest solar-to-electricity conversion efficiency (eta) of 2.11 +/- 0.06%, which is higher than that of the cell with sputtered-Au-CE (1.64 +/- 0.06%). This is due to the higher electrocatalytic ability of the TiC-NPs for reducing the polysulfide (S-x(2-)) ions and the lower charge-transfer resistance at the interface of the CE and the electrolyte. Meanwhile, the three-dimensional structure of the Ti-based ceramic materials also acts as an extended charge-transfer surface, which facilitates electron transfer on the CE toward S-x(2-) ions. Explanations are substantiated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and incident photon-to-current conversion efficiency (IPCE) curves. (C) 2013 Elsevier B.V. All rights reserved.